Modeling of Induced Electric Fields as a Function of Cardiac Anatomy and Venous Pacing Lead Location

The combined effects of cardiac anatomy and pacing lead electrode location within left ventricular cardiac veins on resultant pacing thresholds are not well understood. The specific aims of this study were to: (1) develop a comparative electrostatic model based on previously obtained histological measurements, and (2) compare resulting electric fields and voltage gradients with in vitro experimental results. In vitro pacing thresholds measured from swine hearts were utilized to model electric fields generated from different cardiac venous pacing locations within veins of varying diameter and fat thickness. The simulated activation fields were defined as 100 V/m and all materials were defined as isotropic. The obtained results predicted larger activation fields when an electrode was oriented away from the myocardium or in free-floating positions, hence requiring more myocardial tissue to have 100 V/m than when it was oriented toward the myocardium. Thus, the resultant modeled electric fields followed the same qualitative trends as in vitro experiments performed in the swine hearts. In general, while electrode position primarily affected pacing thresholds, both vein diameter and relative epicardial fat thickness also influenced pacing thresholds. The electric fields were larger for basal regions modeled using larger vein diameters and epicardial fat thicknesses. These electrostatic field simulations provide unique insights as to how varied cardiac anatomies and relative electrode locations affect thresholds by enabling visualization of the electric fields propagating through cardiac tissues during pacing from the venous system.